Method for producing bisphenol alcoxylates

ABSTRACT

A process for preparing bisphenol alkoxylates comprises reacting at least one bisphenol with alkylene oxide in the presence of a phosphine catalyst which is essentially free of alkali metal hydroxide.

The present invention relates to a process for preparing bisphenolalkoxylates, in particular bisphenol A alkoxylates. In addition theinvention relates to the use of catalysts employed for this purpose.

Bisphenol alkoxylates are used for a wide variety of applications, forexample for the synthesis of polyester resins (JP 59012-934-A) andpolyurethanes (JP 59197-417-A).

Bisphenol alkoxylates, in particular bisphenol A alkoxylates, areprepared, as is known to those skilled in the art, from bisphenol A byreaction with an alkylene oxide, e.g. ethylene oxide, propylene oxide orbutylene oxide (JP 60243-036-A), in the presence of a catalyst.Catalysts used are, in particular, alkali metal hydroxides such assodium hydroxide, potassium hydroxide or tertiary amines (see the abovementioned JP publications and also Shanghai Inst. Chem. Technol.,Shanghai in Chemical Abstracts 94:48110).

The alkoxylation reaction can lead to different addition products. Theknown catalysts, for instance, lead to a product in which the additionproducts have a relatively broad molar mass distribution.

If a high reaction selectivity is desired, solvents are sometimes usedin order to influence the selectivity of the alkylene oxide additiononto bisphenol A in the desired direction (U.S. Pat. No. 4,846,996).However, this measure leads to a reduction in the space-time yield,since the solvent used has to be removed again after the reaction iscomplete.

Another possible way of solving the problem is to allow the reaction ofa phenol with an alkylene oxide to proceed in the presence ofphosphonium halides as catalysts, in the presence or absence of asolvent.(JP AS 654/75; DE-A 2 157 455).

A further measure to obtain a bisphenol A addition product having anarrow molar mass distribution is crystallization of the product.However, this step likewise reduces the space-time yield andadditionally leads to reduced yields.

Sheng Zhicong et al. [Shang-hai Hua Kung Hsueh Yuan Hsueh Pao 1980, 48(1), 92] describe studies on the reaction of propylene oxide withbisphenol A. It is stated that the preferred catalyst is NaOH and thatthe amount of catalyst can be reduced if concomitant use is made of aLewis base such as triethylamine or triphenylphosphine (i.e. the Lewisbase is used as cocatalyst). However, further information which wouldenable a person skilled in the art to carry out the reaction is lackingin this publication. In addition, there is the undesirable effect thatthe catalyst loses its activity toward the end of the reaction and thebisphenol A monopropoxylate content is increased as a consequence.

A low selectivity is therefore to be expected when using other alkyleneoxides, too. This applies especially to ethylene oxide, since ethyleneoxide is significantly more reactive than propylene oxide. A personskilled in the art would therefore expect the formation of multiplyethoxylated products and thus a broader molar mass distribution.

It is an object of the present invention to provide a process forpreparing bisphenol alkoxylates, in particular bisphenol A alkoxylates,which gives, dialkoxylated products with high selectivity and in which,in particular, uncontrolled multiple alkoxylation is avoided.

We have found that this object is achieved by a process for preparingbisphenol alkoxylates, which comprises reacting at least one bisphenolwith an alkylene oxide in the presence of a phosphine catalyst.

In a preferred embodiment, the process of the invention is carried outin the absence of solvents, i.e. a mixture, in particular a melt, of thebisphenol and the phosphine catalyst is prepared first and the reactionwith the alkylene oxide is then carried out. However, the reaction canalso be carried out in the presence of an inert solvent. Solvents whichcan be used are, for example, hydrocarbons such as toluene or xylene andketones such as methyl ethyl ketone or diethyl ketone.

Preferred alkylene oxides are C₂-C₄-alkylene oxides, in particularethylene oxide, propylene oxide and 1,2-butylene oxide and mixturesthereof, with particular preference being given to ethylene oxide.Styrene oxide is also suitable.

In the process of the present invention, the catalysts used arematerials belonging to the class of substituted phosphines. These arepreferably selected from the group consisting of substituted phosphinesof the formula (I) below:

where R¹, R² and R³ are aryl radicals of the formula (II) below,

where R⁴ and/or R⁵ can be identical or different and are selected fromamong H, C₁-C₃-alkyl groups, C₁-C₃-alkoxy groups, carboxyl groups andsulfonic acid groups.

Preferred catalysts of the above formula (I) are phosphines in which atleast two of the radicals R¹, R² and R³ are identical. Particularpreference is given to phosphines in which the substituents R¹, R² andR³ are identical.

Very particular preference is given to substituted phosphines in whichthe radicals R¹, R², R³ are phenyl, o-tolyl, m-tolyl or p-tolyl groups.Such particularly preferred phosphine catalysts include, for example,tri-para-tolylphosphine, tri-ortho-tolylphosphine,tris(3-sulfophenyl)phosphine and its salts, in particular the trisodiumsalt, and particularly preferably triphenylphosphine.

The phosphine catalyst can also be employed together with atri-C₁-C₁₂-alkylamine as cocatalyst. The amount of cocatalyst can be upto 35% by weight, based on the total weight of the catalyst. Examples ofcocatalysts are triethylamine, tri-n-propylamine, tri-n-butylamine, etc.

The phosphine catalysts described are particularly suitable for thereaction of bisphenols of the formula

where A is a straight-chain or branched C₁-C₄-alkylene group,

—CH₂OCH₂—, —O— or —S—. Preferably, A is

The OH groups are preferably in the 4 and 4′ positions.

Particular preference is given to bisphenol A(2,2-bis(4-hydroxyphenyl)propane), bisphenol B(2,2-bis(4-hydroxyphenyl)butane), bisphenol C(1,4-bis(4-hydroxyphenyl)cyclohexane) and bisphenol F(2,2′-methylenediphenol).

The alkoxylation products obtained are thus bisphenol alkoxylates of theformula

where A is as defined above, m and n are 0 or 1, with m and n being ableto be identical or different but not both 0, and Alk is a C₂-C₄-alkylenegroup or C₆H₅—CH—CH₂—, in particular —CH₂-CH₂—,

The process of the invention can be illustrated by means of scheme 1below using the reaction of bisphenol A with ethylene oxide as anexample.

A very particular advantage of the process of the invention is the highreaction selectivity, in particular with avoidance of the use of asolvent.

The process of the invention is preferably carried out at from 90° C. to180° C. The pressure is generally in the range from 1 to 50 bar,preferably from 1 to 20 bar, in particular from 2 to 15 bar.

The catalyst is generally used in an amount of from 0.01 to 5% byweight, preferably from 0.1 to 5% by weight, in particular from 0.1 to2% by weight, based on bisphenol used. In general, the reaction iscarried out essentially in the absence of water, i.e. the water contentof the reaction mixture is ≦1% by weight, based on the weight of thereaction mixture.

The amount of alkylene oxide used depends on the product desired. Ingeneral, it is used in an amount of from about 1.9 to 2.5 equivalents,based on bisphenol. After the reaction is complete, the alkylene oxideis removed in a customary manner, e.g. by application of a vacuum.

In a preferred embodiment of the process of the present invention, thebisphenol dialkoxylates obtained in accordance with scheme 1 above areconverted into the corresponding more highly alkoxylated bisphenolalkoxylates in a subsequent reaction with an alkylene oxide (ethyleneoxide, propylene oxide, butylene oxide or styrene oxide). As catalyst,use is made here of an alkali metal hydroxide such as NaOH, KOH, CsOH orLiOH, an alkaline earth metal hydroxide such as magnesium hydroxide orcalcium hydroxide or a DCM catalyst as described, for example, in WO99/16775. The subsequent reaction is illustrated in scheme 2 below usingKOH as catalyst and ethylene oxide:

In this scheme, m and n can be identical or different and be from 0 to20, in particular 0, 1, 2 or 3, with m and n not both being able to be0. It has surprisingly been found that the more highly alkoxylatedcompounds can also be obtained in purer form than is obtained accordingto the prior art. Preference is given to syntheses which lead tocompounds with m=n=1.

The above-described subsequent reaction is carried out under essentiallythe same conditions as the reaction of the bisphenol with the alkyleneoxide.

Bisphenol ethoxylates which can be synthesized by means of the processof the present invention are shown below by way of example:

The invention is illustrated by the following example.

EXAMPLE 1

548 g of bisphenol A and 3.15 g of triphenylphosphine were meltedtogether. 215.8 g of ethylene oxide were subsequently added at from 120to 170° C. over a period of 2.9 hours. After the ethylene oxide had beenfed in, the mixture was stirred within the temperature range indicateduntil the pressure was constant. After application of a vacuum for fromabout 1 to 2 hours, the product (765 g) was drained from the reactor.According to GC analysis, the product contained 92.7% of the compound ofthe formula a) above.

We claim:
 1. A process for preparing bisphenol alkoxylates, whichcomprises reacting at least one bisphenol with an alkylene oxide in thepresence of a substituted phosphine catalyst, the catalyst being free ofalkali metal hydroxide, wherein the substituted phosphine catalyst isselected from the group consisting of substituted phosphines of theformula (I) below:

where R¹, R² and R³ are aryl radicals of the formula (II) below,

where R⁴ and R⁵ are identical or different and are selected from thegroup consisting H, C₁-C₃-alkyl groups, C₁-C₃-alkoxy groups, —COOMgroups and SO₃M groups, where M is H or an alkali metal.
 2. A process asclaimed in claim 1, wherein the reaction is carried out in the melt. 3.A process as claimed in claim 1, wherein in the substituted phosphinecatalysts of the formula (I), the radicals R¹, R² and R³ are identical.4. A process as claimed in claim 1, wherein the radicals R¹, R² and R³are independently selected from the group consisting of phenyl, o-tolyl,m-tolyl, p-tolyl, m-sulfophenyl and sodium m-sulfophenyl.
 5. A processas claimed in claim 4, wherein the substituted phosphine catalyst istriphenylphosphine, tri-o-tolylphosphine or tris(3-sulfophenyl)phosphineor a salt thereof.
 6. A process as claimed in claim 1 wherein thebisphenol is of the formula

where A is a straight-chain or branched C₁-C₄-alkylene group,

 —CH₂OCH₂—, —O— or —S—.
 7. A process for preparing a bisphenol multiplealkoxylate comprising preparing a bisphenol di-monoalkoxylate first byreacting at least one bisphenol with an alkylene oxide in the presenceof a substituted phosphine catalyst, the catalyst being free of alkalimetal hydroxide, to produce the bisphenol di-monoalkoxylate, and thenreacting the bisphenol di-monoalkoxylate with an alkylene oxide to formthe multiple alkoxylate of the formula (II) below

where m and n are identical or different and are 0, 1, 2 or 3, with mand n not both being able to be 0, and Alk¹ and Alk², which are can beidentical or different, are C₂-C₄-alkylene or Ph—CH—CH₂— or combinationsthereof.
 8. A process as claimed in claim 1, wherein the alkylene oxideis ethylene oxide.
 9. A process as claimed in claim 4, wherein thealkylene oxide is ethylene oxide.
 10. A process as claimed in claim 9,wherein the bisphenol is bisphenol A and the substituted phosphinecatalyst is triphenyl phosphine.
 11. A process as claimed in claim 1,wherein a tri-C₁-C₁₂-alkylamine cocatalyst is employed with thephosphine catalyst in an amount up to 35% by weight, based on the totalweight of the catalyst.
 12. A process as claimed in claim 7, wherein thesubstituted phosphine catalyst is selected from the group consisting ofsubstituted phosphines of the formula (I) below:

where R¹, R² and R³ are aryl radicals of the formula (II) below,

where R⁴ and R⁵ are identical or different and are selected from thegroup consisting H, C₁-C₃-alkyl groups, C₁-C₃-alkoxy groups, —COOMgroups and SO₃M groups, where M is H or an alkali metal.
 13. A processas claimed in claim 12, wherein in the substituted phosphine catalystsof the formula (I), the radicals R¹, R² and R³ are identical.
 14. Aprocess as claimed in claim 13, wherein the radicals R¹, R² and R³ areindependently selected from the group consisting of phenyl, o-tolyl,m-tolyl, p-tolyl, m-sulfophenyl and sodium m-sulfophenyl.
 15. A processas claimed in claim 14, wherein the substituted phosphine catalyst istriphenylphosphine, tri-o-tolylphosphine or tris(3-sulfophenyl)phosphineor a salt thereof.
 16. A process as claimed in claim 15 wherein thebisphenol is of the formula

where A is a straight-chain or branched C₁-C₄-alkylene group,

 —CH₂OCH₂—, —O— or —S—.
 17. A process according to claim 16, wherein thealkylene oxide is ethylene oxide.